ext4 crypto: exit cleanly if ext4_derive_key_aes() fails

commit d76d99b2 upstream.

Return value of ext4_derive_key_aes() is stored but not used.
Add test to exit cleanly if ext4_derive_key_aes() fail.
Also fix coverity CID 1309760.
Signed-off-by: Laurent Navet <laurent.navet@gmail.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

fs/ext4/crypto_key.c

@@ -230,6 +230,8 @@ int _ext4_get_encryption_info(struct inode *inode)
 	}
 	res = ext4_derive_key_aes(ctx.nonce, master_key->raw,
 				  raw_key);
+	if (res)
+		goto out;
 got_key:
 	ctfm = crypto_alloc_ablkcipher(cipher_str, 0, 0);
 	if (!ctfm || IS_ERR(ctfm)) {